Eiter, Thomas, and Rafael Kiesel. “On the Complexity of Sum-of-Products Problems over Semirings”. Proceedings of the AAAI Conference on Artificial Intelligence 35, no. 7 (May 18, 2021): 6304–6311. Accessed May 9, 2026. https://ojs.aaai.org/index.php/AAAI/article/view/16783.